How are the diseases like fever, cough, and cold etc. classified in contrast to diseases like diabetes, hypertension, and asthma etc.?

In almost every Out patient department or a clinic often a febrile illness (fever) without an initially obvious etiology (sometimes called fever without localizing signs) as fever of unknown origin (FUO).

Defining this is based upon simple conditions:

Fever higher than 38.3ºC on several occasions.

Duration of fever for at least three weeks

Uncertain diagnosis after one week of study in the hospital

Later the classification can be pruned down to specific classification based upon:

●History

●Physical examination

●Complete blood count, including differential and platelet count

●Blood cultures (three sets drawn from different sites with an interval of at least several hours between each set; in cases in which antibiotics are indicated, all blood cultures should be obtained before administering antibiotics)

●Routine blood chemistries, including liver enzymes and bilirubin

●If liver tests are abnormal, hepatitis A, B, and C serologies

●Urinalysis, including microscopic examination, and urine culture or a